Various heating devices have been proposed in the past for processing semiconductor wafers during the manufacture of integrated circuit chips. For instance, rapid thermal processing devices are thermal processing chambers where wafers are heated in a small compartment using radiant energy as the energy source. Such systems typically only process a single wafer at a time and include a substrate holder for holding the wafer and a light source that emits light energy for heating the wafer. During heat treatment, the semiconductor wafer is heated under controlled conditions according to a preset temperature regime. For monitoring the temperature of the semiconductor wafer during heat treatment, such processing chambers also typically include temperature sensing devices, such as pyrometers, that sense the radiation being emitted by a semiconductor wafer at a selected band or wavelength. By sensing the thermal radiation being emitted by the wafer, the temperature of the wafer can be calculated with reasonable accuracy.
In alternative embodiments, instead of or in addition to using radiation sensing devices, thermal processing chambers can also contain thermocouples for monitoring the temperature of the wafers. Thermocouples measure the temperature of objects by direct contact.
Many semiconductor heating processes require a wafer to be heated to high temperatures so that various chemical and physical reactions can take place as the wafer is fabricated into a device. During thermal processing, semiconductor wafers are typically heated to temperatures of from about 200° C. to about 1300° C., for times that are typically less than a few minutes.
Rapid thermal processing chambers that heat the wafers using light energy typically operate in a non-equilibrium state. Specifically, the walls surrounding the wafer are kept cool and thus the chambers are typically referred to as “cold wall” systems. The non-equilibrium configuration refers to the fact that the filament temperature inside the radiant source is at a much higher temperature than the wafer. The key advantage of using rapid thermal processing systems is the ability to quickly change wafer temperature therefore enabling very short heating cycles. A drawback to rapid thermal processing systems, however, is the cost per wafer processed, especially for cycles greater than one minute, since most systems are only equipped to heat one wafer at a time.
Thermal processing systems capable of processing a plurality of semiconductor wafers have been proposed. For instance, U.S. Pat. No. 6,051,512 discloses an apparatus and method for rapid thermal processing of a plurality of semiconductor wafers, which is incorporated herein by reference. The '512 patent has provided great advances in the art in that multiple wafers can be processed during a single heat cycle. The present disclosure is directed to further improvements in thermal processing chambers for processing multiple wafers simultaneously.